A role for the sarcoplasmic reticulum in Ca2+ extrusion from rabbit inferior vena cava smooth muscle.
Ca2+ extrusion from rabbit inferior vena cava smooth muscle was studied using ratiometric fura 2 fluorimetry. Concomitant blockade of the plasma membrane Ca(2+)-adenosinetriphosphatase (ATPase; PCMA), Na(+)-Ca2+ exchanger, and sarcoendoplasmic reticulum Ca(2+)-ATPase (SERCA) completely prevented the decline in intracellular Ca2+ concentration ([Ca2+)]i) normally observed when Ca2+ is removed from the extracellular space (ECS) after stimulated Ca2+ influx. Blockade of the Na(+)-Ca2+ exchanger by removal of external Na+ reduced the rate of [Ca2+]i decline by 47%. Blockade of SERCA with cyclopiazonic acid reduced it by 23%, and this was not additive to the effects of Na+ removal. Exposure to nominally Ca(2+)-free solution prevented the sarcoplasmic reticulum (SR) from reloading only if the Na(+)-Ca2+ exchanger was operational. Our results can be explained by an SR contribution to Ca2+ extrusion in which SERCA is arranged in series with Na(+)-Ca2+ exchange.
Nazer
M A
MA
Department of Pharmacology and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, Canada.
Van Breemen
C
C
D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D008955:Models, Cardiovascular; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D010656:Phenylephrine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000502:physiology*; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors; D014665:Vasodilator Agents / Q000494:pharmacology; D014682:Vena Cava, Inferior / Q000502:physiology*
D007211:Indoles; D019831:Sodium-Calcium Exchanger; D014665:Vasodilator Agents; D010656:Phenylephrine; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D004533:Egtazic Acid; D015759:Ionomycin; D000252:Calcium-Transporting ATPases; D011188:Potassium; D002118:Calcium; C000543:cyclopiazonic acid